Stabilization of gasoline and of addition agents therefor



Patented Nov. 12, 1946 STABILIZATION OF GASOLINE AND OF ADDITION AGENTSTHEREFOR Daniel B. Luten, Jr., Berkeley, Calif., assigno'r to ShellDevelopment Company, San Francisco, Calif., a corporation of Delaware NoDrawing. Application January 17, 1944, Serial No. 518,667

11 Claims.

This invention is based on the finding of the unique and unusualproperties of certain ortho, para or di-alkyl phenols in stabilizingcertain substances commonly employed as motor fuel or gasolineadditives. In particular, it pertains to the stabilization of aromaticamines and to the stabilization of hydrocarbon compositions such asgasoline which contain these amines alone or in combination with metalantiknock additives such as tetra alkyl lead, metallic carbonyls, etc.

It is an object of the invention to produce stabilized aromatichydrocarbon amines. These stabilized or inhibited aromatic amines may bedissolved in gasoline or other motor fuel; hence, it is an object of theinvention to provide motor fuels containing aromatic amino compoundswhich fuels are stabilized against oxidation or decomposition. Anotherpurpose is to provide motor fuels containing tetra alkyl lead and/ormetallic carbonyl compounds which compounds are stabilized by theadditives of the present invention. An additional object is to provideimproved motor fuels such as aviation' gasoline having high antiknockratings and improved oxidation or storage stability. Further objectswill be apparent from the following description.

Aromatic amino compounds, upon exposure to air, often exhibit a tendencyto change color as their period of contact with oxygen lengthens. Thiscolor change is the first noticeable symptom of oxidative decompositionwhich, since it is catalytic in nature, proceeds, if unchecked, at anaccelerated rate until the amino compounds are entirely altered incomposition and usefulness.

A particular employment for aromatic amino compounds, especially thoseof low molecular weight, is in motor fuels such as gasoline in whichthey exert a beneficial anti-knock effect. It will be appreciated,therefore, that if such aromatic amines are produced for incorporationin gasoline, it is especially desirable that they be stabilized againstoxidation, since if such decomposition sets in either before or aftertheir addition to the base fuel, it will not only decrease their ownvalue as a fuel component but may also promote the decomposition of thebase fuel,

resulting in gum formation, increased knock rating, volatility changesetc.

Aromatic amines have also been added to cracked gasolines in smallquantities in order to decrease the gum forming tendencies of thegasoline. Since such inhibition of the oxidation of the gasoline isachieved by the preferential oxidation of the amino inhibitor, it willbe realized how difficult it may be to find a substance which willstabilize such aromatic amines themselves, both before and after theiraddition to'gasoline.

For this problem, the broad class of known gasoline inhibitors has beenfound ineffective.

Indeed many of them act as pro-oxidants or oxidation accelerators forthe amino compounds. Commonly used gasoline stabilizers which were foundto be pro-oxidantsfor aromatic amines in- 19 clude: para benzyl aminophenol, alpha-naphthol,

4-tertiary butyl catechol, hydroquinone, pyrogallol, beta-naphthol, paraphenylene diamine and diphenyl phenylene diamine. Other pro oxidantsubstances include thiophenol, thiodiglycollic acid, FeS, sulfanilicacid, salicyclic acid,

brom benzene, dianisidine,-iodine, iron or galvanized iron surfaces,sodium nitrite, benzoyl peroxide, lead peroxide, copper phenylpropionate, manganese oleate and stannous chloride.

Gasoline inhibitors which were found to be without inhibiting eflfect onaromatic amines include: phenyl alpha naphthylamine, mixtures ofcresylic acids boiling between about 220 C. and 240 C., 2,3,5,6-tetramethyl phenol, penta-methyl phenol, 2,3,5-trimethyl phenol, para, paradihydroxy diphenyl, guaiacol, durohydroquinone, thymol, resorcinol,anthraquinone, etc.

It has now been found, however, that a particular group of di-alkylphenols in which the alkyl groups are attached at the 2 and 4 or ortboand para positions, as hereafter more fully described, have uniquestabilizing properties for aromatic amino compounds, either when theamines are alone or when they are dissolved in gasoline. The stabilizingagents of the present invention are dialkyl phenols in which the 4 orpara position and one ortho position (2 or 6) are occupiedbya primary,secondary or tertiary alkyl radical. Only one of the alkyl radicals maybe 40 tertiary, however, so one may have a di-primary alkyl,di-secondary alkyl, mono-primary monosecondary alkyl, mono-tertiarymono-primary alkyl, or mono-tertiary mono-secondary alkyl' phenol.

The ortho and para alkyl radicals (only one of which, as just stated,being a tertiary alkyl) may conveniently be methyl, ethyl, n-propyl,isopropyl, n-, iso-,' secondary and tertiary butyl,'

and the various primary, secondary or tertiary amyl, hexyl, heptyl,octyl, and homologous radicals. In general, radicals containing not morethan about 16 or 20 carbonatoms are preferred, those 2,4 di-alkylphenols containing a total of not more than about 12 carbon atoms in allalkyl groups being particularly desirable (i. e. those having a maximumof about 18 carbon atoms counting the nuclear'carbon atoms). The alkylradicals should generally be such as to render the phenols soluble inthe composition to which they are added. Too high a number of carbonatoms causes the compounds to be waxy and diflicultly soluble. However,particularly in gasolines of appreciable aromatic contents, phenols withrelatively large wax radicals containing up to say 35 or 40 or even morecarbon atoms may be suitable, especially if those radicals containbranched chains. The ortho or para radicals may also comprise one ormore aromatic groups such as phenyl, tolyl, benzyl, etc., althoughstrictly aliphatic radicals are generally superior.

The above limitations regarding the nature and placement of the severalhydrocarbon radicals on the phenol are very important. In thisconnection, it is of interest that 2,4,6-tri tertiary alkyl phenols, forexample 2,4,6-tri tertiary butyl phenol, have little anti-oxidant valuefor aromatic amines-some phenols are worse than no inhibitor at all.Thus, some tri alkyl phenols found to be pro-oxidants for aromaticamines are 2,6-ditertiary butyl-4-methyl or -ethyl phenols,2,6-dimethyl-4-tertiary butyl pheno, 2,5-dimethyl-4-tertiary butylphenol and 2,4-ditertiary butyl-5-methyl phenol.

The aromatic amines generally added to gasoline for their antiknockvalue are usually mononuclear monoamines having not more than a.

higher'nuclearly alkylated anilines (which may.

also be substituted on the N'atom), such as toluidines, xylidines,cymidine, cumidine, pseudo cumidine, etc., as well as suitablesubstituted derivatives. Mixtures of aromatic amines, as well as theindividual amines, may be employed and tion of colored products andoxidation of the xylidine occur simultaneously on aging, the decrease oflight transmitted through the solution is an indication of the extent ofoxidation. The following determinations were made at 70 0., oneatmosphere of air and employing inhibitor concentrations of 0.2% byweight.

amines, such as the earlier enumerated monocycle monocyclic aromaticamines having less than a total of about 7 carbon atoms in all alkylgroups,

exhibit an inhibiting or stabilizing efiect on gasoline, which efiect isgreater than the calculated total of the inhibition produced by eachadditive alone. This effect is particularly noticeable in saturate orinitially stable gasoline such as aviation gasoline composed of straightrun, cyclopentane,- aromatics, alkylate, hydroformed fractions and thelike, which initially stable gasoline has been rendered unstable by theincorporation of tetra alkyl lead.

Another tri alkyl phenol, 2,4-dimethyl-6-tertiary butyl phenol is asingularly successful inhibitor of tetra alkyl lead fluid or ofinitially stable gasoline composed of saturate fraction (such asenumerated above) which gasoline has been rendered unstable by tetraalkyl lead. This phenol will also inhibit the oxidation of the presentaromatic amines. Hence when stabilizing amine-containing leaded gasolineor aromatic poly-amines may also be used. Likewise, aromatic-richpetroleum fractions may be nitrated and reduced to give mixtures such asdescribed in U. S. Patents 1,844,362 and 2,252,099, which mixtures maybe blended in a motor fuel according to the present invention.

However, the di-alkyl phenolic inhibitors will also stabilizemcnonuclear amines having a greater number of carbon atoms thanindicated above, i. e. greater than 6, as well as poly-cyclic aromatichydrocarbon amines, e. g. various naphthylamines, alkyl naphthylamines,aryl naphthylamines, anthracylamines and the like.

It is understood that the inhibitor must be well distributed throughoutthe substance to be protected. Thus, it the amine is a liquid undernormal conditions, the inhibitor should be intrue or colloidal solution.If it is a solid, the inhibitor may be incorporated by first melting theamine, distributing the necessary amount of inhibitor as by dissolvingit, and then allowing the mixture to solidify; or else by merelyspraying the inhibitor or a solution thereof onto the solid amine. Inundiluted aromatic amines, the content of the poly alkyl phenol mayrange from about 0.01% to 1% (by weight), preferably about 0.1% toQuantitative determinations of the effectiveness of inhibitors of thepresent invention in stabilizing xylidine were made by determining thelight transmission through various xylidine samples for a specific wavelength 0:550 mu) using a Coleman spectrophotometer. Since theformaamines which are later to be incorporated into leaded gasoline (inparticular into saturated type gasoline such as aviation gasoline) itmay be advantageous to employ 2,4-dimethyl-6-tertiary butyl phenoltogether with a dialkyl phenol of the present invention. Thus, forexample, the tetra ethyl lead will be stabilized by the2,4-dimethyI-G-tertiary butyl phenol while the aromatic amines will bestabilized by one or more of the present dialkyl phenols such as2-tertiary butyl- 4-methyl phenol, Z-tertiary butyl-4-ethyl phenol,2,4-dimethyl phenol, 2-inethyl-4-tertiary butyl phenol, etc.

Effective total amounts of the poly alkyi phenolic inhibitors in agasoline are generally between about 0.001% to 0.1% (by weight), apreferred range being from about 0.001% to about 0.01% or 0.1%. Thearomatic amines may be employed in about 0.25% to 3% (by volume) in agasoline although higher or lower quantities can also be used. The upperlimit is usually prescribed by maximum boiling range specifications ofthe gasolines. Since the amines are relatively high boiling, they mayraise the upper boiling range of the gasoline above permissible limitsit used in excessive amounts. On the other hand, amounts efl'ect whenapplied particularly to saturated,

' like.

tallic carbonyls in gasoline may often be per-- initially stablegasolines rendered unstable by the addition of metal antiknockcompounds, as well as to unsaturated, initially unstable gasolines (suchas cracked gasolines). with or without metal anti-knock compounds. Up toabout 6 cc. per gallon of tetra ethyl lead or anequivalent amount ofanother tetra alkyl lead may normally be added to gasoline.

Solubilizers for the aromatic amines may also be present, particularlyin gasolines which contain but a small amount of aromatic constituents.Such mutual solvents may be low molecular weight'alcohols, ethers,ketones (in particular five or six carbon atom unsymmetrical ketones)aromatics such as benzene, toluene, etc. i 1 A further advantage in theuse of the combination of aromatic amine and poly alkyl phenol is thatwhen the inhibitor efiectiveness of the compounds begins to wear off, asharp break in the induction period does not occur, but rather theformation of deterioration products proceeds slowly and a visibleprecipitate forms only after extended aging. This is in marked contrastto the action of most oxidation inhibitors whose efiectiveness isusually terminated quite suddenly at the end of their period ofstabilization with the rapid formation of degradation products in thegasoline and the consequent prompt termination of the usefulness of themotor fuel.

It has also been found that the combination of the present poly alkylphenols withv aromatic amines shows extraordinary stabilizing power formetallic carbonyl compounds contained in gasoline or other motor fuel.

It is known that numerous metallic carbonyl compounds possess desirableantiknock properties when incorporated in a hydrocarbon fuel. However,various difliculties have beset their particular utilization, notableamong which has been their chemical instability and ease ofdecomposition on standing, as well as their tendency to catalyze thebreakdown of the hydrocarbon fuel, producing such efiects as gumformation and the Although the anti-knock function of meformed in partby other compounds such as tetra ethyl lead, there are particularapplications in which such other substances are not applicable as in abreak in fuel or in a heavily leaded fuel to which the addition of moretetra alkyl lead would have little effect.

Metallic carbonylic compounds contemplated by the present applicationare, for example, the various carbonylic compoundsof iron, nickel,cobalt, molybdenum, mercury, etc., as well as their various applicablederivatives. Among these may be mentioned Fe(CO)4, Fe(CO)5, FE4(CO)15NO,FeNi(CO)9, Ni(CO)4, Co(CO)3NO, M(CO)s, Hg(Co(CO)4)2. under engineconditions to produce metallic carbonyls may also be employed, such ascomplexes of carbonyls with ammonia, amines, alkanol amines, etc.

In general, an amount of metallic carbonylic compound in the range ofabout 0.25 to 3 'cc./gallon is adequate for a break-in fuel,'although upto about cc./gallon may be used. In addition, there may be present upto-about 6 cc. of commercial tetra alkyl lead per gallon as well asvarious solutizers such as alcohols, ketones, esters, pyridine, aromaticconstituents such as benzene and the like.

About 0.001% to 0.1% by weight of the alkylated phenol in associationwith about 0.25% to 3% by volume aromatic amine is generally adequate tostabilize the metallic carbonyl in a gasoline. Particularly when tetraalkyl lead is also present, a part of'the phenolic inhibitor content maybe 2,4-dimethyl-6-tertiary butyl phenol.

The invention claimed is: v

1. A composition comprising hydrocarbons containing a knock-reducingamount of a mononuclear aromatic amine in which the total number ofcarbon atoms in all alkyl radicals is less than 7 and a stabilizingamount of a 2,4-dialkyl phenol in which one alkyl substituent isselected from the group consisting of primary, secondary nd tertiaryalkyl radicals and the other alkyl substituent is selected from thegroup consisting of primary and secondary alkyl radicals.

2. A composition comprising hydrocarbons containing a knock-reducingamount of a mononuolear aromatic amine in which the total number ofcarbon atoms in all alkyl radicals is less than 7 and a stabilizingamount of a 2,4-dialkyl phenol having a maximum of about 18 carbon atomsand in which one alkyl substituent is selected from the group consistingof primary, secondary and tertiary alkyl radicals and the other alkylsubstituent is selected from the group con-.

sisting of primary and secondary alkyl radicals.

3. A composititon comprising hydrocarbons containing about 0.25% to 3%(by volume) of a mononuclear aromatic amine in which'the total number ofcarbon atoms in all alkyl radicals is less than 7 and about 0.001% to0.1% (by weight) of a 2,4-dialkyl phenol in which one alkyl substituentis selected from the group consisting of Compounds which decompose ofprimary,

the group consisting of primary, secondary and tertiary alkyl radicalsand the other alkyl substituent is selected from the group consisting ofprimary and secondary alkyl radicals.

4. A composititon comprising gasoline hydrocarbons containinga tetraalkyl lead compound, a knock-reducing amount of a mononuclear aromaticamine in which the total number of carbon atoms in all alkyl radicals isless than 7 and a stabilizing amount of a 2,4-dialkyl phenol V having amaximum of about 18 carbon atoms and in which one alkyl substituentisselected from the group consisting of primary, secondary and tertiaryalkyl radicals and the other alkyl substituent is selected from thegroup consisting, of primary and secondary alkyl radicals.

5. A composition of matter comprising a mixture of gasoline hydrocarbonswhich has been rendered potentially unstable by the addition of tetraalkyl lead, about 0.25% to 3% (by volume) of a mononuclear aromaticamine in which the total number of-carbon atoms in all alkyl radicals isless than 7 and a total of about 0.001% to 0.1% (by weight) of twophenols, one of which is 2,4- dimethyl-G-tertiary butyl phenol and theother being a 2,4-dialkyl phenol having a maximum of about 18 carbonatoms and in which one alkyl substituent is selected from the groupconsisting and the other alkyl substituent is selected from primary andsecondary alkyl radicals.

6. A composition comprising gasoline hydrocarbons containing up to about6 cc. tetra ethyl lead per gallon of-said composition, about 0.25% to 3%(by volume) of xylidine and about 0.001% to 0.1% (byweight) of a mixtureof 2,4-dimethyl- (i-tertiary butyl phenol and 2-tertiary butyl-4- methylphenol.

secondary and tertiary alkyl radicals,

and a total of about 0.01% to 1% (based on the xylidine weight) of2,4-dimethyl-6-tertiary butyl phenol and a 2,4-dialkyl phenol having amaximum of about 18 carbon atoms and in which one alkyl substituent isselected from the group consisting of primary, secondary and tertiaryalkyl carbons containing iron carbonyl and tetra alkyl lead whichcomposition is stabilized by a mononuclear aromatic amine in which thetotal num- 'ber of carbon atoms in all alkyl radicals is less than 7, by2,4-dimethyl-6-tertiary butyl phenol and by a 2,4-dialkyl phenol havinga maximum of about 12 carbon atoms in all alkyi radicals and in whichone alkyl substituent is selected from the group consisting of primary,secondary-and tertiary alkyl radicals and the other alkyl substituent isselected from the group consisting of primary and secondary alkylradicals.

10. A composition consisting essentially of a mixture of normally stablesaturated hydrocarbon fuels containing a knock-reducing amount of amononuclear aromatic amine in which the total number of carbon atoms inall alkyl radicals is less than 7 and a stabilizing amount of a2,4-dialkyl phenol in which one alkyl substituent is selected from thegroup consisting of primary, secondary and tertiary alkyl radicals andthe other alkyl substituent is selected from the group gzoanliisting ofprimary and secondary alkyl rad- 11. A composition consistingessentially of a mixture of normally stable saturated hydrocarbon fuelscontaining an amount of tetra alkyl lead sufiicient to render itrelatively unstable on storage, about 0.25% to 3% (by volume) of amononuclear aromatic amine in which the total number of carbon atoms inall alkyl radicals is less than 7 and a total of about 0.001% to 0.1%(by weight) of two phenols, one of which is 2,4- dimethyl-G-tertiarybutyl phenol and the other being a 2,4-dialkyl phenol having a maximumof about 18 carbon atoms and in which one alkyl substituent is selectedfrom the group consisting of primary, secondary and tertiary alkyiradicals, and the other alkyl substituent is selected from the groupconsisting of primary and secondary alkyl radicals.

DANIEL B. LU'I'EN, J a.

